Conventional techniques for precipitating particles from solution include methods in which a solution is heated in a container to evaporate off and remove the solvent and obtain particles (hereunder referred to as “dry evaporation methods”), methods in which a solution is sprayed into hot air to evaporate the solvent in a gas phase, and precipitate particles as a dry powder (hereunder referred to as “spray dry methods”), and methods in which a solution of a solute dissolved in a good solvent is added dropwise to a heated poor solvent and the good solvent is evaporated off, to obtain a slurry of the particles and the poor solvent (hereunder referred to as “common methods using a good solvent and poor solvent”).
Specific examples of common methods using a good solvent and poor solvent are described in PTL 1 (Japanese Unexamined Patent Publication HEI No. 7-316087). PTL 1 discloses a method for producing 2,2-bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]propane (hereunder abbreviated as TBA-BP), in the form of needle crystals that have excellent thermal stability and storage stability, as well as an improved powder flow property.
Dry evaporation methods, spray dry methods and common methods using a good solvent and poor solvent are all employed as methods for precipitating particles. In such methods, the rate of solvent evaporation is relatively slow. Therefore, the particles precipitate slowly by crystal growth, and it is difficult to obtain particles with low crystal growth. In addition, when particles are precipitated from a solution in which a plurality of raw material components have been dissolved, the raw material components precipitate as separate crystals with low solubility, and it is therefore difficult to obtain fine particles with the different raw material components in a complexed state.
The aforementioned methods are therefore poorly efficient when the goal is to produce fine particles comprising different raw material components in a complexed state.